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Stages of melanoma

Men and women discussing melanoma skin cancer

This page tells you about staging for melanoma skin cancer. You can find information about

 

A quick guide to what's on this page

The stages of melanoma

The stage of a melanoma describes how deeply it has grown into the skin, and whether it has spread. In the UK 8 out of 10 melanomas (80%) are found at an early stage when the chance of cure is very high. It is important to know the stage because doctors will often use it to decide on the kind of tests and treatment you need, and the likely risk of the melanoma coming back after treatment.

The different systems doctors use

Doctors use a number of different systems and scales to describe the stages of melanoma. Further down this page, there is information about two scales that are used, called the Clark scale and the Breslow scale. These measure how deeply the melanoma has spread into the skin.

TNM staging system

TNM stands for Tumour, Node, Metastasis. T describes the size and depth of the melanoma. N tells you whether or not melanoma cells have spread to the lymph nodes. And M tells you whether or not it has spread to the rest of the body.

Number stages of melanoma

Using the TNM classification, melanomas are grouped into number stages from 0 to 4. Stage 0 means the melanoma cells are only in the top surface layer of skin cells. It is also called in situ melanoma. Stages 1 and 2 are the earlier stages, where the cancer has not spread. In stage 3 it has spread to the lymph nodes or the lymphatic vessels. Stage 4 melanomas have spread elsewhere in the body, away from where they started.

 

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What staging is

The stage of a melanoma describes how deeply it has grown into the skin, and whether it has spread. The tests you have to diagnose your melanoma will give some information about the stage. In the UK, most melanomas are found at an early stage when the chance of cure is very high. It is important to know how deeply the melanoma has gone into the skin because doctors use this to decide on

  • The kind of treatment you need
  • The likely risk of the melanoma coming back after treatment
  • Whether you need tests to see if the melanoma has spread into lymph nodes close to the melanoma
 

Types of melanoma staging systems

Doctors use a number of different systems and scales to describe the stages of melanoma

  • The Clark scale looks at how deeply the melanoma has gone into the different layers of the skin
  • The Breslow scale measures the thickness of the melanoma in the skin
  • TNM staging of melanoma describes the thickness of the melanoma and whether there is any spread to lymph nodes or other parts of the body
  • Number stages of melanoma group together the depth of the melanoma and the TNM staging in a simpler way

Doctors in the UK tend to mostly use TNM staging because it describes the stage of melanoma in the most specific way. For treatment decisions and when talking about stage to patients, doctors tend to use the simpler system of number stages. There is more information about all these staging systems below.

 

Melanoma thickness (Breslow and Clark scales)

There are 2 scales that look at how deeply the melanoma has gone into the skin. These are called the

When doctors remove a melanoma they send it to a laboratory. A pathologist then examines the melanoma and looks at how deeply it has gone into the skin. These days, it is more common for doctors  to use the Breslow scale than the Clark scale, when they are staging melanoma. 

The Clark scale

You might hear your doctor talk about Clark levels. This is a way of measuring how deeply the melanoma has grown into the skin and which levels of the skin are affected. You can see the main layers of the skin in this diagram.

Diagram showing the structure of the skin

Here are what the different levels of the Clark scale mean

  • Level 1 is also called melanoma in situ – the melanoma cells are only in the outer layer of the skin (the epidermis)
  • Level 2 means there are melanoma cells in the layer directly under the epidermis (the papillary dermis)
  • Level 3 means the melanoma cells are throughout the papillary dermis and touching on the next layer down (the reticular dermis)
  • Level 4 means the melanoma has spread into the reticular or deep dermis
  • Level 5 means the melanoma has grown into the layer of fat under the skin (subcutaneous fat)

It is important not to confuse Clark levels with the TNM stage or number stage (described lower down this page). The Clark levels only look at the depth of melanoma cells in the skin. The number stage is looking at whether the melanoma has spread to lymph nodes or another part of the body.

The Breslow scale

For the Breslow scale, a pathologist measures the thickness of the melanoma with a small ruler, called a micrometer. Doctors use a scale called the primary tumour thickness scale, or the Breslow thickness. It measures in millimetres (mm) how far the melanoma cells have reached down through the skin from the surface. You can see the structure of the skin in the diagram above. The Breslow thickness is used in the TNM staging system for melanoma.

 

TNM staging of melanoma

TNM stands for Tumour, Node, and Metastases. This staging system describes the size of a primary tumour (T), whether any lymph nodes contain cancer cells (N) and whether the cancer has spread to another part of the body (M).  The T part of the TNM describes the thickness of the melanoma (primary tumour) according to the Breslow scale

There are 5 stages of tumour size in melanoma

  • Tis – melanoma cells are only in the very top layer of the skin surface
  • T1 – the melanoma is less than 1 millimetre thick
  • T2 – the melanoma is between 1 mm and 2 mm thick
  • T3 – the melanoma is between 2 mm and 4 mm thick
  • T4 – the melanoma is more than 4 mm thick

Diagram showing the T stages of melanoma

The T part of the TNM system is further divided into two groups, a and b, depending on whether the melanoma is ulcerated or not. Ulcerated means that the covering layer of skin over the tumour is broken. The letter a means not ulcerated and b means ulcerated. So, for example, a melanoma may be T3a or T3b. Ulcerated melanomas have a higher risk of spreading than those which are not ulcerated.

There are 4 possible stages describing whether cancer cells are in the nearby lymph nodes or lymphatic ducts

  • N0 – there are no melanoma cells in the nearby lymph nodes
  • N1 – there are melanoma cells in one lymph node
  • N2 – there are melanoma cells in 2 or 3 lymph nodes
  • N3 – there are melanoma cells in 4 or more lymph nodes

The N part of the stage is further divided into groups a, b and c. If the cancer in the lymph node can only be seen with a microscope (micrometastasis) it is classed as a. But if there are obvious signs of cancer in the lymph node (macrometastasis) it is classed as b. 

The letter c means that there are melanoma cells in small areas of skin very close to the primary melanoma or in the skin lymph channels. These groups of melanoma cells in the skin are called satellite metastases. Melanoma cells in the lymph channels are called in transit metastases.

M0 means the cancer has not spread to another part of the body. M1 means the cancer has spread to another part of the body. 

M1 is further divided into 

  • M1a – melanoma cells have spread to skin in other parts of the body or to lymph nodes far away from the where the melanoma started growing
  • M1b – melanoma cells have spread to the lung
  • M1c – melanoma cells have spread to other organs or cause high blood levels of a chemical made by the liver (lactate dehydrogenase)

Nearly everyone in the UK with a newly diagnosed melanoma will only have a T stage. This means that the melanoma has not spread to any lymph nodes or any other part of the body.

In a very small number of people, after a melanoma has been removed, nodules of melanoma may appear in the skin close to the area of the original melanoma. This is called local recurrence. It occurs when some melanoma cells have broken away from the primary tumour and begun to grow new tumours (nodules) in the surrounding skin. This can happen at any time after the original melanoma has been removed. So it could be some years later. The more time that has gone by since your original diagnosis, the less likely this is to happen.

 

Number stages of melanoma

There are 5 main stages in this system. They are 

Stage 0 (in situ melanoma)

This means the melanoma cells are only in the top surface layer of skin cells (the epidermis) and have not started to spread into deeper layers.

Stage 1A

The melanoma is less than 1mm thick. The covering layer of skin over the tumour is not broken – it is not ulcerated. The melanoma is only in the skin and there is no sign that it has spread to lymph nodes or other parts of the body.

Stage 1B

The melanoma is less than 1mm thick and the skin is broken (ulcerated). Or it is between 1 and 2mm and is not ulcerated. The melanoma is only in the skin and there is no sign that it has spread to lymph nodes or other parts of the body.

There is information about the treatment of stage one melanomas in this section.

Stage 2A

The melanoma is between 1 and 2 mm thick and is ulcerated. Or it is between 2 and 4mm and is not ulcerated. The melanoma is only in the skin and there is no sign that it has spread to lymph nodes or other parts of the body.

Stage 2B

The melanoma is between 2 and 4mm thick and is ulcerated. Or it is thicker than 4mm and is not ulcerated. The melanoma is only in the skin and there is no sign that it has spread to lymph nodes or other parts of the body.

Stage 2C

The melanoma is thicker than 4mm and is ulcerated. The melanoma is only in the skin and there is no sign that it has spread to lymph nodes or other parts of the body.

There is information about treatment of stage 2 melanomas in this section.

Stage 3A

The melanoma has spread into up to 3 lymph nodes near the primary tumour. But the nodes are not enlarged and the cells can only be seen under a microscope. The melanoma is not ulcerated and has not spread to other areas of the body.

Stage 3B

Stage 3B means that 

  • The melanoma is ulcerated and has spread to between 1 and 3 lymph nodes nearby but the nodes are not enlarged and the cells can only be seen under a microscope OR
  • The melanoma is not ulcerated and it has spread to between 1 and 3 lymph nodes nearby and the lymph nodes are enlarged OR
  • The melanoma is not ulcerated, has spread to small areas of skin or lymphatic channels, but nearby lymph nodes do not contain melanoma cells

Stage 3C

Stage 3C means that 

  • There are melanoma cells in the lymph nodes and small areas of melanoma cells in the skin or lymph channels close to the main melanoma OR
  • The melanoma is ulcerated and has spread to between 1 and 3 lymph nodes nearby which are enlarged OR
  • The melanoma may or may not be ulcerated and has spread to 4 or more nearby lymph nodes OR
  • The melanoma may or may not be ulcerated and has spread to lymph nodes that have joined together

There is information about treatment of stage 3 melanomas in this section.

Stage 4

These melanomas have spread elsewhere in the body, away from where they started (the primary site) and the nearby lymph nodes. The most common places for melanoma to spread are the lung, liver or brain or to distant lymph nodes or areas of the skin. There is information about treatment of stage 4 melanomas in this section.

In the UK, most melanomas are early stage 1 and are completely cured with surgery. Most stage 2 tumours can also be cured with surgery.

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Updated: 17 January 2014